1. Field of the Invention
The invention relates to a battery module in which a plurality of battery cells (secondary batteries) capable of charging and discharging are connected in series, a method of fabricating the battery module, and a vehicle having the battery module. More particularly, the invention is concerned with the construction of battery cells that constitute a battery module suitable for installation on a vehicle.
2. Description of the Related Art
Battery modules each constructed by connecting a plurality of battery cells in series are provided which use lightweight lithium-ion batteries having a high energy density or other secondary batteries or storage devices, such as capacitors, as the cells. It has been found increasingly important to use such battery modules as power supplies that can provide high power, more specifically, as power supplies to be installed on vehicles or power supplies for personal computers and portable terminals. In particular, a battery module in which a plurality of cells in the form of lightweight lithium-ion batteries having a high energy density are connected in series is expected to be used as a high-power power supply to be installed on a vehicle. As an electrode body mounted in each of the cells that constitute the battery module, a rolled electrode body formed by rolling a long-length sheet-like anode collector, a long-length sheet-like cathode collector and a long-length sheet-like separator(s) into a flat shape is used. For example, Japanese Patent Application Publication No. 11-167929 (JP-A-11-167929), Japanese Patent Application Publication No. 2000-285953 (JP-A-2000-285953) and Japanese Patent Application Publication No. 2002-8708 (JP-A-2002-8708) disclose secondary batteries (cells) having such flat-shaped rolled electrode bodies.
In the meantime, the battery module, when installed on a vehicle, such as an automobile, is mounted in a limited space, and is assumed to be used in conditions where vibrations occur; therefore, the battery module is assembled such that a large number of cells are arranged into an array, and are brought into a restrained condition. When the cells are held in the restrained condition, a substantial load is applied to the individual cells that constitute the battery module. Accordingly, the cells that constitute the battery module are desired to provide good charge-discharge characteristics and output characteristics and have long service life even in the condition where such a large load is applied to the cells.